MCP73830 datasheet(13/22 Pages) MICROCHIP

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DS20005049D-page 13

MCP73830/L

6.0

APPLICATIONS

The MCP73830 is designed to operate in conjunction

with a host microcontroller or in stand-alone applica-

tions. The MCP73830/L provides the preferred charge

algorithm for dual Lithium-Ion or Lithium-Polymer cell’s

constant

current,

followed

constant

voltage.

Figure 6-1 depicts a typical stand-alone application

circuit, while Figure 6-2 depicts the accompanying

charge profile.

FIGURE 6-1:

Typical Application Circuit.

FIGURE 6-2:

Typical Charge Profile

(Li-Ion Battery).

6.1

Application Circuit Design

Due to the low efficiency of linear charging, the most

important factors are thermal design and cost, which

are a direct function of the input voltage, output current

and thermal impedance between the battery charger

and the ambient cooling air. The worst-case situation is

when the device has transitioned from Preconditioning

mode to Constant Current mode. In this situation, the

battery charger has to dissipate the maximum power. A

trade-off must be made between the charge current,

cost and thermal requirements of the charger.

6.1.1

COMPONENT SELECTION

Selection of the external components in Figure 6-1 is

crucial to the integrity and reliability of the charging

system. The following discussion is intended as a guide

for the component selection process.

6.1.1.1

Charge Current

The preferred fast charge current for Li-Ion/Li-Poly cells

is below the 1C rate, with an absolute maximum current

at the 2C rate. The recommended fast charge

current should be obtained from the battery

manufacturer. For example, a 500 mAh battery pack

with 0.7C preferred fast charge current has a charge

current of 350 mA. Charging at this rate provides the

shortest charge cycle times without degradation to the

battery pack performance or life.

6.1.1.2

Input Over Voltage Protection

(IOVP)

Input over voltage protection must be used when the

input power source is hot-pluggable. This includes USB

cables and wall-type power supplies. The cabling of

these supplies acts as an inductor. When the supplies

are connected/disconnected from the system, large

voltage transients are created which may damage the

system circuitry. These transients should be snubbed

out. A transzorb - unidirectional or bidirectional - con-

nected from the V+ input supply connector to the 0V

ground reference will snub the transients. An example

of this can be seen in Figure 6-3.

STAT

VDD

VBAT

PROG

Regulated

wall cube

4.7µF



1-Cell

Li-Ion

Battery

VSS

4.7 µF



MCP73830/L

Note:

Please consult with your battery supplier,

or refer to the battery data sheet, for the

preferred charge rate.

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